The frenzy for the much touted Anya Hindmarch £5 "I'm not a plastic bag" bag was not entirely unexpected, as any diligent pupil of supply and demand economics could have told you.

The formula goes something like this: take a trendy designer, get some even trendier Hollywood heart-throbs to be photographed casually lugging the designer's wares and add a charity and some cunning PR. Oh, and only release 4,000 of them (at least initially). The result, of course, is huge overdemand ... and more press coverage.

The organisers of the project claim to want to reduce plastic bag consumption, but the manner of the launch provokes a number of questions. However well-meaning, how helpful is a waste reduction plan that triggers an episode of mass consumption? How many of the people queuing in the cold will use their bags on the shopping run? What effect will the new bag have on Britain's annual consumption of 8bn plastic bags? Will it help people think more about environmental issues? And what good is thinking alone?

The demand for the bags has already forced the not-for-profit organisation We Are What We Do - the charity producing the bag - into rearguard action, promising that the supply of bags has not run out and there's no need to hand over your money to people profiteering (ironically enough) by selling them on eBay at more than 10 times the stated price.

If the charity's site has crashed when you visit it, you'll get this:

"Hello everyone, Due to enormous and unprecedented demand for the Anya Hindmarch/We Are What We Do bag, we are currently experiencing problems with our website ...The bags have not yet sold out so please don't be persuaded to pay over the odds for a bag through Ebay (or any other auction site) in the meantime!"

The 11,000 people who have registered an interest in the bag, meanwhile, are receiving emails saying there are only 2,800 left. If you're one of the lucky few, the price now appears to be £10 (it comes with a book) plus a £5.52 delivery charge. More bags are expected to be available in Sainsbury's at the end of next month. But be aware that none of your money goes to good causes.

So, rather than spend your free time queuing in the pursuit of celebrity-endorsed commodities, why not knit your own carrier from waste plastic bags? (Sample instructions here.) Just don't scoop up a pile of unused bags at the supermarket checkout to use as raw material.